1. Field of the Invention
The present invention relates to apparatus and processes for the fabrication of a microelectronic substrate. In particular, the present invention relates to a fabrication technology that encapsulates at least one microelectronic die within a microelectronic substrate core or that encapsulates at least one microelectronic die (without a microelectronic substrate core) to form a microelectronic substrate.
2. State of the Art
Substrates which connect individual microelectronic devices exist in virtually all recently manufactured electronic equipment. These substrates are generally printed circuit boards. Printed circuit boards are basically dielectric substrates with metallic traces formed in or upon the dielectric substrate. One type of printed circuit board is a single-sided board. As shown in FIG. 20, single-sided board 200 consists of a dielectric substrate 202, such as an FR4 material, epoxy resins, polyimides, triazine resins, and the like, having conductive traces 204, such as copper, aluminum, and the like, on one side (i.e., first surface 206), wherein the conductive traces 204 electrically interconnect microelectronic devices 208 (shown as flip-chips) attached to the first surface 206. However, single-sided boards 200 result in relatively long conductive traces 204 which, in turn, results in slower speeds and performance. Single-sided boards 200 also require substantial surface area for the routing of the conductive traces 204 to interconnect the various microelectronic devices 208 which increases the size of the resulting assembly.
It is, of course, understood that the depiction of the dielectric substrate 202, the conductive traces 204, and the microelectronic devices 208 in FIG. 20 (and subsequently FIGS. 21 and 22) are merely for illustration purposes and certain dimensions are greatly exaggerated to show the concept, rather than accurate details thereof.
Double-sided boards 210 were developed to help alleviate the problem with relatively long conductive traces. As shown in FIG. 21, the double-sided board 210 comprises a dielectric substrate 202 having conductive traces 204 on the dielectric substrate first surface 206 and on a dielectric substrate second surface 212. At least one electrically conductive via 214 extends through the dielectric substrate 202 to connect at least one conductive trace 204 on the first surface 206 with at least one conductive trace 204 on the second surface 212. Thus, the microelectronic devices 208 on the dielectric substrate first surface 206 and on the dielectric substrate second surface 212 may be in electrical communication. The electrically conductive vias 214 are generally plated through-hole vias and may be formed in any manner known in the art.
FIG. 22 illustrates another board design, known as a multi-layer board 220. A multi-layer board 220 comprises two or more pieces of dielectric material (shown as first dielectric material 222 and second dielectric material 224) with conductive traces 204 thereon and therebetween with electrically conductive vias 214 formed through the first dielectric material 222 and the second dielectric material 224. This design allows for shorter traces and reduced surface area requirements for conductive trace 204 routing.
Although such boards have been adequate for past and current microelectronic device applications, the need for higher performance and shorter traces of substrate boards increases as the speed and performance of the microelectronic devices increases. Therefore, it would be advantageous to develop new substrates/boards, which achieve higher speed and performance.